The present invention relates to sputtering processes, and more particularly, to an improved ion beam sputtering process for producing multilayer optical coatings, and the like.
One conventional sputtering process is known as magnetron sputtering. The operating pressure of the magnetron sputtering process is relatively high, which provides for a relatively low mean free path. While the magnetron sputtering process can be conducted at relatively high rates, higher pressures used in this process result in poor film structure. A better understanding the this conventional magnetron sputtering process may be had from a reading of a book by "J. Vossen and W. Kern entitled "Thin Film Processes", Academic Press (1978)", for example.
The assignee of the present invention has employed a conventional ion beam sputtering process to produce optical coatings, and the like. This conventional ion beam sputtering process produces superior quality optical coatings that have low absorption, high packing density, good step coverage, and may comprise novel coating materials. However, this conventional ion beam sputtering process a relatively slow process. Using this conventional ion beam sputtering process, deposition rates are on the order of 1 .ANG./second, which results in deposition times of around 40 hours for a typical dielectric reflector coating, for example. Consequently, in order to complete a multilayer coating within a reasonable length of time, sputtering yield must be increased to achieve a deposition rate of approximately 5 .ANG./second. This would allow the fabrication of multilayer coatings in approximately 8 hours, thereby making the ion beam sputtering process a commercially viable process. The present invention has been developed to produce these desired improvements.
Therefore, it is an objective of the present invention to provide for an improved ion beam sputtering process for producing multilayer optical coatings, and the like. It is a further objective of the present invention to provide for an ion beam sputtering process that adds energy to surface atoms of a sputtering target to increase deposition rates and improve the sputtering yield of the process.